SPARTA, Ky. — An early accident Sunday in the NASCAR race at Kentucky turned Brad Keselowski’s hopes of repeating as winner into a 33rd-place finish, knocking him from the top 10 in his bid to defend his Sprint Cup championship.

Keselowski was running near the top 10 on lap 49 when Kurt Busch’s No. 78 Chevy went low, came back up the track and into his left rear quarter-panel. The contact spun the No. 2 Ford up the track in the front stretch and triggered a wreck collecting five other cars.

Greg Biffle’s No. 16 Ford had nowhere to go and got the worst of it, slamming into Keselowski and lifting his car off the asphalt and into the outside retaining wall. Biffle’s mangled car caught fire, but he and Keselowski weren’t injured.

The incident sent Keselowski’s car to the garage and the driver later tweeted, “we ain’t done” before returning to the race on lap 154. He eventually finished 114 laps behind winner Matt Kenseth.

Busch, who was sixth, apologized for causing the wreck. Keselowski seemed to accept it, though it didn’t change the outcome.

“I’m still wrecked,” he said, sitting in a golf cart outside the track’s care center. “He’s smarter than that, he knows better than that.”

The accident spoiled what had been a great tripleheader weekend for the Michigan native. Keselowski won Friday night’s Nationwide Series race and was second in Thursday’s Truck race, efforts that made him a threat in Sunday’s 400-miler rescheduled to Sunday because of rain Saturday night.

Keselowski started eighth and was either in or near the top 10 for the first 45 laps before Busch appeared to run over a drain before coming back on to the track and into him.

“I know he didn’t intentionally wreck me, but it’s one of those things,” Keselowski said. “A chain of events with the way the cars drive and the track’s got that really bad bump down there, and we all know that. There’s no reason to go down there, but he still did.”

Dave Blaney, Paul Menard, Landon Cassill and Travis Kvapil also were involved in the wreck along with Biffle, who also returned to the race and finished 34th.

“I don’t know what happened there,” said Biffle, who avoided an earlier incident when Kyle Busch spun out. “We weren’t fortunate to miss this one. I was trying to get to the bottom to miss (Keselowski) and couldn’t get it. I was on the brakes and the nose might have been on the race track or something. I couldn’t get to the bottom to miss him.”

Keselowski entered the race ninth in points, looking to get things going and hopefully earn his first win of the season at a track where he thrives.

The Penske Racing driver was still optimistic despite another setback in a season that has included two NASCAR penalties totaling 31 points.

Asked if he would change his approach with nine races left before the Chase, Keselowski said, “Nope. We’re just going to do our thing and we’re just on a streak of bad luck. It will turn around and when it does, we’ll be in victory lane and be all right.”